Core box for sand cores



ea. 4, 1962 w. B. JAY 3,066,363

CORE BOX FOR SAND CORES Filed Sept. 14, 1959 3 Sheets-Sheet l IN V EN-TOR.

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El 4, 1962 w. B. JAY

CORE BOX FOR SAND CORES 3 Sheets-Sheet 2 Filed Sept. 14, 1959 wv Mu INVENTOR- 0 5 Jay Decn 4, 1962 w. B. JAY 3,066,363

CORE BOX FOR SAND CORES Filed Sept. 14, 1959 is Sheets-Sheet 5 IN V EN TOR.

Bfihha'idd Fatented Dec. 4, 1962 3,066,363 CQEE EBGX FOR SAND CQRES Wiiiard day, Dearborn, Mich. Filed Sept. id, 1959, Ser. No. 8393678 Til Qiaims. {Cl. 22-16) This invention relates to improvements in core box for sand cores. The principal objects of this invenLion are:

First, to provide an improved core box for the formation of sand cores for metal castings which core box can be rapidly and uniformly filled with sand to form cores of various shapes and which can be rapidly and eii'ectively cleaned of sand accumulations after each molding operation by means of compressed air delivered th ough distribution channels within the core box itself.

Second, to provide a core box having a novel arrangement of vents for the escape of air trapped in the mold cavity and introduced thereinto during the molding operation, which vents are also capable of introducing cleaning air and lubricants and core treating gases into the core box during the molding operation or oscillating sand in the cavity to polish and break in the box.

Third, to provide a core box with a novel form of blow tip for introducing sand to be molded more directly to all portions of the core being formed.

Fourth, to provide a core box with an upper part having a blow plate and upper core box plate separated by the heads of blow tips or sand nozzles extending through the core plate in such a manner as to leave exhaust vents or passages from within the core chamber to the exterior of the core box until the core chamber is entirely filled with its intended charge of sand.

Fifth, to provide a novel form of blow tip or sand nozzle which is easily installed in an upper core plate to form a break-off area directly along the desired upper surface of the core formed in the mold and which is extremely long lived and resistant to the abrasion of the core sand directed therethrough.

Sixth, to provide a mold box for sand cores with a combined upper plate and blow plate for coaction with a conventional sand chamber and compressed air supply in which the blow plate presents only inclined surfaces to the body of molding sand transferred therethrough to prevent the buildup of dead or stationary sand masses and to provide adequate support for center areas of the blow plate which are generally outlined and partially separated from surrounding portions of the blow plate by elongated sand nozzles or blow slots for delivering sand to all portions of an annular core.

Seventh, to provide a mold for forming sand cores which is simple to operate in automatic molding apparatus and which is extremely long lived.

Eight, to provide a core mold box and blow plate which produces superior sand cores by reason of the more direct delivery or" the sand to all portions of the core without swirling motion of the sand or objectionable abrading action on the walls of the core box, and by the provision of means for accurately locating and maintaining the breakofl' areas between the newly formed core and sand remaining in the blow plate.

Other objects and advantages of the invention will be apparent from a consideration of the following description and claims. The drawings, of which there are three sheets, illustrate a highly practical form of the novel core box and sand nozzle or blow tip of the invention as applied to a standard type of core molding machine.

FIG. 1 illustrates somewhat conventionally a familiar type of core molding apparatus with the novel core box of the invention applied thereto and with additional mold blowing and core treating apparatus associated with the novel core box.

FIG. 2 is a fragmentary top plan view of the blow plate, sand nozzles and upper core box plate or cover of the core box of the invention.

FIG. 3 is a fragmentary vertical cross sectional view through the core box of FIG. 2 taken along the plane of the line 33 in FIG. 2.

FIG. 4 is an enlarged top plan view of one of the sand nozzles or blow tips shown in FIGS. 2 and 3.

FIG. 5 is an enlarged side elevational view of the sand nozzle shown in FIG. 4.

FIG. 6 is a fragmentary transverse cross sectional view through the sand nozzle taken along the. plane of the line 66 in FIG. 5.

As is well known many cast metal objects such as internal combustion blocks are formed with substantially inclosed cavities therein for the circulation of cooling liquid around the cylinder bores of the engine. These cavities are formed in the metal casting operation which forms the engine block by providing relatively solid sand cores molded to the proper Shape and positioned in the metal mold to exclude molten metal from the desired areas in the metal mold. It is common practice to form these sand cores in the desired generally cylindrical shape and provided with suitable binding for the sand so that the sand core will function properly in the metal casting mold. This means that a preliminary molding or casting operation is necessary to form the sand cores in the desired shape and for this purpose sand core boxes and molding machines are relatively common in the foundry art.

FIG. 1 illustrates somewhat conventionally a semiautomatic sand molding machine in which a lower part of a core mold box 1 is supported on a suitable vertical reciprocable table 2 for elevation into coacting closed relationship with the bottom of an upper core box part or plate 3. Prior to being elevated by the table 2 the lower core box part 1 is vertically supported on the rollers 4- or a transfer rail 5. The table: 2 is adapted to be elevated by the piston 6 of a fluid actuated squeeze cylinder 7. The piston 6 raises the core part i into selected relation with the upper core part or plate 3 and this plate is in turn connected to a blow plate 8 secured to the underside of a sand chamber Q. The sand chamher 9 is carried by a carriage plate lit? slidably supported on the rolls 11 to shift the carriage plate and the sand refill port 12 therein to underneath a sand supply chute 3.3 or an air pressure supply duct lid.

The sand chamber and carriage plate are reciprocated between charge and delivery positions by the carriage plate operating cylinder 15. The lower part i. of the core box is reciprocable horizontally onto and ofif of r the transfer track 5 to one or the other sets of supporting rolls 15 or CtSA on opposite sides of the rollover cylinder 16 of a core drawing machine. The core box l is reciprocated by the piston 17 of a cylinder 18, and normally two or more lower core box parts 1 are provided so that one core molding box can be filled while another is having the freshly molded core withdrawn therefrom.

The rollover cylinder 16 receives a core box on its upper side and a core dryer or cover plate 19 is secured over the newly molded core by a suitable clamp iii. The rollover cylinder is then inverted to place the core box in upside down position over the vertically reciprocable core draw bars 21 carried by an upright draw cylinder 22. The draw bars 21 are elevated to support the core dryer or cover plate 1? after which the clamps it; are released and the newly formed core lowered from the inverted core box by the draw bars 21. The empty core box is cleaned of residual sand during which time another core box is being filled and a core molded therein and the new core box shifted to the empty upwardly facing side of the rollover cylinder. Thus far the structure described is generally conventional in molding shops and is described mainly to point out the purpose of the novel features of the invention.

As appears more clearly from FIGS. 2 and 3, the lower part of the core mold box 1 has a bottom wall 23 having openings or holes 24 formed therein at spaced intervals depending upon the shape and size of the core to be formed. A bottom plate 25 closes off the lower ends of the holes 24 but passages 26 formed in the bottom wall connect the chambers formed by the holes to a laterally opening port 2'7 on the side of the mold box. The holes or openings 24 receive and locate the necks of cylin drical metal core members .29 which form and define the inner surface of the sand cores to be formed. T he metal cores 29 are hollow with vent chambers 34) therein communicating through the necks 28 with the chambers A plurality of angled vent passages Ell connect the cen tral chambers 36 with annular collecting grooves 32 formed around the undersides of the metal core cylinders 2?.

The extreme outer edges of the cylinders 29 outside of the collecting grooves 32 are cut or ground away slightly to provide thin vent passages 33 opening from the surface of the metal core to the passages 31. The vent passages 33 are wide enough to permit the flow of air therethrough but are still narrow enough to prevent the passage of molding sand into the vent passages. Similar upper inclined vent passages and slots 35 at the upper ends of the metal cores vent the upper ends of the sand core chambers 37. The sand core chambers 37 are defined by the walls '36 of the lower part of the core box located in desired spaced relation to the metal cores 29 or by two adjacent metal cores. As appears from the different thicknesses of the sand core chambers 37 in FIG. 3 these chambers can be made in any desired shape or size by proper proportioning and positioning the walls of the core box and the metal cores therein.

The upper part or cover 3 of the core box is secured to the bottom of the sand chamber 9 as by cap screws 38 and has a central recess 39 formed in its upper surface. The lower wall 4% and face of the cover defines locater holes 41 which receive upstanding pins 42 mounted on the tops of the cores 29 to locate the lower part ll of the core box relative to the cover when the two parts of the core box are joined by elevation of the table 2. The lower wall also defines a plurality of slots 43 and 44 with downwardly converging inclined side walls positioned over the selected portions of the sand core chamber 37. Some of the slots 43 are curved to conform to curved sections of the core chamber while other slots such as 44 may be straight where the core chamber permits this configuration.

Positioned in each of the slots 43 and 44 is a wear nozzle 45 formed of fused ceramic or other material highly resistant to abrasion. It will be understood that the wear nozzle conforms in shape to the slot in which it is positioned. The nozzles 45 define elongated blow slots 46 with downwardly converging wide walls so that the blow slots taper downwardly in width. The nozzles 45 are carefully sized to fit snugly in the slots 43 and 44 with the lower ends of the nozzles spaced upwardly from the lower face of the cover and opening into shallow core recesses 47 in the cover plate so that part of the sand core formed in the core box is formed in the cover above the lower part 1 of the core box.

The side walls of the wear nozzles 45 are provided with vertically extending laterally projecting ribs 48 at spaced points therearound and the surfaces of these ribs contact the converging surfaces of the slots 43 and 4-;- leaving thin vent passages 49 opening from the core chambers 37 to the recessed face of the cover. The height or projection of the ribs 4-8 is accurately controlled so that the thickness of the vent passages 49 is less than the thick ness of the grains of sand used in the core molding operation so that while air can escape through the vents no core sand can work its way into the vents.

The upper ends of the blow nozzles 45 are provided with integral laterally projecting flanges 59 which rest upon the upper recessed surfaces of the cover 3. These flanges Sil define laterally and downwardly opening grooves 51 which communicate with the vent passages 49. The blow nozzles 45 are held down in the slots 4.344 and against the recessed surface of the cover 3 by a blow plate 52 which fits into the recess 39 in the cover. The blow plate 52 and the recess 39 in the cover are oppositely shouldered as at 53 and the dimension of the blow plate from the shoulder to its lower face is accurately controlled to just touch the upper ends of the blow nozzles 45 and hold them firmly in the slots 4344. The space between the lower surface of the blow plate and the upper recessed surface or" the cover 3 thus forms a chamber 54 communicating with the upper ends of the vent passages 51 and 49. A laterally opening port 55 in the side of the cover 3 communicates with the chamber 54% for purposes which will be described in detail presently.

In the formation of cylindrical sand cores as for internal combustion engine blocks the central areas 551 of the blow plate 52 above the centers of the core chambers are substantially separated from surrounding areas of the blow plate by the series of blow slots 43 and 44. In order to support these central areas 551 the thickness of the blow plate between the slots 43 and 44 is increased by the formation of radially extending ridges 56 to provide an increased thickness of metal for resisting the pressure of the sand and air applied through the sand during the molding operation. hese ribs or areas of in creased thickness 56 perform an additional function of forming downwardly inclined surfaces 57 completely around the slots 43 and M in the cover 3. The inclined surfaces 57 extend to and merge with the more sharply inclined side walls of delivery slots 58 which open at their lower ends to the tops of the blow slots 46 in the nozzles 45. It will thus be seen that from the upper surface of the blow plate 52 to the lower ends of the blow slots 46, the core sand in the sand chamber is at all times supported by a surface of more or less inclined shape and position. This means that the downwardly directed air pressure in the sand chamber will continually cause all portions of the charge of sand to move downwardly toward the blow slots 46 and into the core chamber. There are no fiat areas on the top of the blow plate where core sand can accumulate and harden to interfere with successive core molding operations. At the same time central areas of the blow plate partially separated from the surrounding parts of the plate are adequately supported to resist the pressures existing in the sand chamber.

Another feature of the wear nozzle 45 appears most clearly in FIG. 6 in which it is shown that the lower end of the blow slot as is curved or converged as at 59 to provide a wearing edge of increased lateral thickness. The undersurface of the blow nozzle below the wearing edge is downwardly concave as at so in continuation of the surface of the core chamber 47 in the cover 3 to form a smooth upper edge on the sand core formed in the core bodies. The curved edge or lip 59 along the bottom of the blow slot performs two functions, the first of which is to provide increased material in the blow nozzle at the point of greatest wear therein. Since all of the sand necessary to form the core and fill the core chambers must pass through the blow slots 46 the greatest wear on the blow nozzles will occur at the constricted lower ends of the blow slots and the converged edges 59 provide additional material at this point which must be worn away before a blow nozzle has to be replaced. A second function of the thickened lip 59 .l is to reduce the width of the sand sprue which projects from the newly formed sand core into the blow slots 46 and which must be broken off cleanly when the upper part or cover 3 of the mold box is separated from the lower part it by reducing the width of the blow slot 46 at the converging edges 59. The thickness of this sprue is locally reduced forming a natural breaking or parting plane which separates the edge of the newly formed sand core from the remaining body of sand in the blow nozzles and the sand chamber.

The sequence of operation of the core molding apparatus with the novel form of core box is as follows. The sand chamber carried by the carriage plate 1f is moved under the sand chute 13 by the carriage plate cylinder 151 to receive a charge of molding sand. The sand is impregnated with a suitable binder as is common. The sand chamber 9 with the blow plate 52 and core box cover 3 attached thereto is then returned into registry with the air pressure supply pipe 14 and a clean empty core box 1 is pressed upwardly by the table 2 and squeeze cylinder 7 into registering interlocked engagement with the cover Air pressure is then applied from the supply conduit lid to the sand chamber to force the charge of molding sand downwardly through the delivery slots 53 and the blow nozzles into the core chamber 37. As was pointed out the raised ribs as on the surface of the blow plate support the central areas 551 of the blow plate and also form continually inclined surfaces along which the charge of sand slides easily toward the blow nozzles 4-5. By keeping the entire mass of sand in the sand chamber moving it is possible to reduce the pressure required from the air supply 14 in order to effect the complete transfer of the sand to the core box.

in passing through the elongated blow slots as to the core chamber, the sand is delivered directly downwardly to substantially all areas in the core chamber 3'7 and little lateral movement of the sand is required to fill all portions of the core chamber. The sand emerging through the blow slots 6 is directed primarily downwardly and not swirl or impinge directly on the side walls of the core chamber 37 so that wear of the mold parts is reduced. Air initially present in the core chamber 37 escapes through the thin vent slots 33 and f to the passages 3l-3d and the air chambers 3'!) within the cylindrical cores 2%. From there the air is exhausted through the chambers 24 and connecting passages 216 to the exhaust port 27 so that back pressure in the core chamber does not interfere with a complete molding operation. As the sand builds up and covers the upper vent slots and commences to fill the core chambers $7 in the cover entrapped air and air intrained in the molding sand can still escape through the inclined vent passages 49 alongside of the blow nozzles 45 to the chamber below the blow plate from where it is vented through the port 55. With the charging or molding operation complete, the lower part 1 of the core box is lovered away from the cover 3 and the sand sprues break neatly along the curved edge at the bottom of the blow slots 46.

After the core parts are separated two simultaneous operations take place. The sand chamber and cover 3 of the core box move to the left in PEG. 1 to receive a second charge of sand, but prior to receiving the sand the nozzle at is advanced by the cylinder 62 into engagement with the port 55 and air from the conduit 63 is applied to the upper core part to blow reversely through the chamber 54-, notches Sit and vent passages to clean out any sand which may have stuck to the lower ends of the vent passages l The upper part or cover of the core is thus quickly cleaned for a second molding operation.

The lower part or box 1 of the core mold is advanced by the piston rod 17 on the transfer track 5 to the rollers on the rollover cylinder and provided with a core dryer plate 19 and inverted as previously explained and after the core is drawn onto the core draw bar 21, the nozzle 64 is advanced into engagement with the port 27 to reversely blow air through the passages 26, chambers and 3b to the vent passages 31-34 and slots 33-35. This blow out air cleans the lower core box 1 and if desired a lubricant for the surfaces of the mold box can be introduced through the nozzle 64.

-fhile the inverted lower core box 1 is being emptied and cleaned a previously cleaned core box on the opposite side of the rollover cylinder ll? can be moved to the table 2. to start a second molding operation. The nozzle 65 can be advanced into engagement with the port 27 for the purpose of further cleaning the lower core box or for introducing a gas such as C0 for treating the newly formed sand core in the core mold box. The core mold box with the blow slot nozzles therein is thus easily cl ed and extremely long lived in use and provides a superior sand core by reducing erosion and rough surfaces on the mold box surfaces and producing a clean areal; between the molded core and the sprue sand in the blow nozzles.

The arrangem nt of vents in the core box has an additional ft..ctonal advantage that is useful during breaking in or polishing of the finished box. A small charge of dry polishing sand, say 10% of the total volume of the mold cavity, can be put in. the bottoms of the several cavities 3? and a closure plate or seal clamped over the blow slots Then an air jet can be introduced intermittently through t This ne port 27 and passage 26. causes the dry to be blown up to the top of the cavity and fall back down when the jet is turned off. The vertical oscillating motion of the dry sand provides a finish polish on all surfaces of the mold cavity and the polishing motion of the dry sand provides a finish polish on all surfaces of the mold cavity. The polishing motion is in the same desired direction as will be followed by the char ng movement of the core sand when the box is put into service. The narrow vent passages 33, 35 and prevent the polishing sand from escaping. By using an automatic on-oif air valve the polishing and breaking in can be accomplished without attention and at little expense, and a smoothly operating core box is assured.

What is claimed as new is:

l. Molding apparatus for sand cores comprising an upper mold part plate with an upwardly shouldered recess in its upper face and with a core forming groove formed in its lo ver face, said groove being curved in part in the contour of the core to be formed, said upper part defining a plurality of downwardly converging slots opening at spaced intervals to the top of said groove, wear resistant fused ceramic nozzles fitted in said slots and having continuously downwardly converging inclined outer and inner walls defining blow slots with inwardly curved wear tips on their lower edges, laterally projecting ribs on the outsides of said nozzles engaging the sides of the slots in said upper part whereby vent passages thinner than a grain of sand being molded are formed between the outer sides of the nozzles and the surfaces of said slots, laterally projecting flanges on the upper ends of said nozzles supported on the upper surface of said upper part and defining downwardly opening grooves opening between the upper ends of said vent passages and the edges of said flanges, a blow plate positioned in the recess of said upper part and havin a flange located by the shoulder on said upper part to rest the bottom of the blow plate on the tops of said nozzles whereby the bottom of the blow plate and the top of the upper part define a cham her, said upper part defining a blow-out port opening to said chamber, a bottom mold box part defining a recess with a central hole in the bottom, a hollow cylindrical core member positioned in said recess with its periphery spaced therefrom to define a sand core chamber registering with the core groove in said top part, locater studs on each end of said core member received in the hole spouses in the bottom of the lower part of said mold box and a hole provided therefor in the bottom of said top part, the lower stud being hollow and opening to the interior of the core member, vent passages extending angularly from the hollow inside of said core member to adjacent the end edges of the core member, the peripheral edges of said core members terminating in slightly spaced relation to said mold parts to form vent slots narrower than a grain of molding sand and opening to said vent passages, said lower mold box part defining a port opening to said hollow stud, said blow plate defining a plurali'ty of downwardly converging delivery slots opening to and conforming with the blow slots in said nozzles, and upwardly inclined surfaces radiating from all sides of said delivery slots at a lesser angle than the sides of said delivery slots, said inclined surfaces forming a peak within the contour of said core chamber and radiating ridges between adjacent slots in the blow plate.

2. Molding apparatus for sand cores comprising an upper mold part, said upper part defining a plurality of downwardly converging slots opening at spaced intervals to the top of the core chamber of the part to be molded, wear resistant nozzles fitted in said slots and having downwardly converging inclined inner Walls defining blow slots, laterally projecting ribs on the outsides of said noz zles engaging the sides of the slots in said upper part whereby vent passages thinner than a grain of sand being molded are formed between the outer sides of the nozzles and the surfaces of said slots, laterally projecting flanges on the upper ends of said nozzles supported on the up-- per surface of said upper part and defining downwardly opening grooves opening between the upper ends of said vent passages and the edges of said flanges, a blow plate positioned on said upper part and located by said upper part whereby the bottom of tie blow plate and the top of the upper part define a chamber, said upper part defining a blow-out opening to said chamber, a bottom mold part defining a recess, a hollow core member positioned in said recess with its periphery spaced therefrom to define a sand core chamber registering with the slots in said top part, locater studs at each end of said core member engaged with the bottom of the lower part of said mold and the bottom of said top part, one of said studs being hollow and opening to the interior of the adjacent core part, vent passages extending angularly from the hollow inside of said core member to adjacent the end edges of the core member, the peripheral edges of said core member terminating in slightly spaced relation to said mold parts to form vent slots narrower than a grain of molding sand and opening to said vent passages, one of said mold parts defining a port opening to said hollow stud, said blow plate defining a plurality of downwardly converging delivery slots opening to and conforming with the blow slots in said nozzles, and upwardly inclined surfaces radiating from all sides of said delivery slots at a lesser angle than the sides of said delivery slots, said inclined surfaces forming a peak within the contour of said core chamber and radiating ridges between adjacent slots in the blow plate.

3. Molding apparatus for sand cores comprising an upper mold part plate with an upwardly shouldered recess in its upper face and with a plurality of core forming grooves formed in its lower face, said grooves being curved in part and intersecting in the contour of the core to be formed, said upper part defining a plurality of down wardly converging slots opening at spaced intervals to the tops of said grooves, wear resistant fused ceramic nozzles fitted in said slots and having downwardly converging inclined inner walls defining blow slots with inwardly curved wear tips on their lower edges, laterally projecting ribs on the outsides of said nozzles engaging the sides of the slots in said upper part whereby vent passages thinner than a grain of sand being molded are formed between the outer sides of the nozzles and the surfaces of said nozzles, laterally projecting flanges on the upper ends of said nozzles supported on the upper surface of said upper part and defining downwardly opening grooves opening between the upper ends of said vent passages and the edges of said flanges, a blow plate p0- sitioned in the recess of said upper part and having a flange located by the shoulder on said upper part to rest the bottom of the blow plate on the tops of said nozzles whereby the bottom of the blow plate and the top of the upper part define a chamber, said upper part defining a blow-out port opening to said chamber, the bottoms of said nozzles being downwardly concave continuations of the core recesses in the bottom of the upper part, a bottom mold box part defining a sand core recess registering with said slots, said blow plate defining a plurality of downwardly converging delivery slots opening to and con forming with the blow slots in said nozzles as co-planar flush continuations of said slots, and upwardly inclined surfaces radiating from all side of said delivery slots at a lesser angle than the sides of said delivery slots, said inclined surfaces forming a peal; within the contour of said core chamber and radiating ridges etween adjacent slots in the blow plate.

4. Molding apparatus for sand cores comprising an upper mold part defining a plurality of downwardly converging slots opening at spaced intervals and arranged in the contour of the core to be molded, wear resistant nozzles fitted in said slots and having downwardly converging inclined inner walls defining blow slots, a blow plate positioned on said upper part, a bottom mold box part defining a recess with a central hole in the bottom, and a hollow core member positioned in said recesses with its periphery spaced therefrom to define a sand core chamber registering with the slots in said top part, 10- cater studs at each end of said core member received in the holes in the bottom of the lower part of said mold box and a hole provided therefor in the bottom of said top part, the lower studs being hollow and opening to the inter or of the core member, vent passages extending angularly from the hollow inside of said core member to adjacent the end edges of the core member, the peripheral edges of said core member terminating in slightly spaced relation to said mold parts to form vent slots narrower than a grain of molding sand and opening to said vent passages, said lower mold part defining a port opening to said hollow stud, said blow plate defining a plurality of downwardly converging delivery slots opening to and conforming with the blow slots in said nozzles.

5. Mold apparatus for making sand cores comprising a lower mold part defining a cavity open at the top, a hollow core member positioned in said cavity in spaced relation to the side walls thereof to form a mold chamher, an upper mold part arranged to fit in contacting relation to the tops of said lower part and said core member, said upper mold part defining a series of elongated slots of downwardly tapered shape arranged in the contour of said core chamber and opening thereto, wear resistant nozzles having downwardly tapering blow slots formed therein positioned in the slots in said upper part, upright ribs on the outer sides of said nozzles seating against the sides of the slots in said upper part and c0- acting therewith to form vent passages opening from said mold chamber, said upper part defining a blow out port communicating with said vent passages, locating studs coacting between said core member and said mold parts, the lower of said studs being hollow and opening b tween the hollow interior of said core member and a coacting blow out passage formed in said lower mold part, said lower mold part defining a blow out port communicating with said blow out passage, the end peripheral edges of said core member being cut back to define grooves with the bottom of said lower mold part and the bottom of said upper mold part of lesser width than the thickness of a grain of molding sand, said core member being formed with vent and blow out passages therein opening between the interior of the core member and said grooves at the ends of the core member, and means including a separate blow plate defining blow slots arranged to deliver mold sand to said slots in said upper part, said plate presenting continuously downwardly inclined surfaces between said slots in said upper part and the top of the blow plate.

6. Mold apparatus for making sand cores comprising a lower mold part defining a cavity open at the top, a core member positioned in said cavity in spaced relation to the side walls thereof to form a mold chamber, an upper mold part arranged to fit in contacting relation to the tops of said lower part and said core member, said upper mold part defining a series of elongated slots of downwardly tapered shape arranged in the contour of said core chamber and opening thereto, wear resistant nozzles having continuously downwardly tapering blow slots formed therein positioned in the slots in said upper part, upright ribs on the outer sides of said nozzles seating against the sides of the slots in said upper part and coacting therewith to form vent passages opening from said mold chamber, said upper part defining a blow out port communicating with said vent passages, said downwardly tapering slots in said nozzles having inwardly converged sides at the bottom forming thickened wear tips.

7. Mold apparatus for making sand cores comprising a lower mold part defining a cavity open at the top, a core member positioned in said cavity in spaced relation to the side walls thereof to form a mold chamber, an upper mold part arranged to fit in contacting relation to the tops of said lower part and said core member, said upper mold part defining a series of elongated slots of downwardly tapered shape arranged in the contour of said core chamber and opening thereto, wear resistant nozzles having downwardly tapering blow slots formed therein positioned in the slots in said upper part, upright ribs on the outer sides of said nozzles seating against the sides of the slots in said upper part and coacting therewith to form vent passages opening from said mold chamber, said upper part defining a blow out port communicating with said vent passages, one end of one wall of said core chamber being cut back to define a groove with the surface of said adjacent mold part of lesser width than the thickness of a grain of molding sand, said lower part being formed with vent and blow out passages therein opening to said groove.

8. Mold apparatus for making sand cores comprising a lower mold part defining a cavity open at the top, a core member positioned in said cavity in spaced relation to the side walls thereof to form a mold chamber, an upper mold part arranged to fit in contacting relation to the tops of said lower part and said core member, said upper mold part defining a series of elongated slots of downwardly tapered shape arranged in the contour of said mold chamber and opening thereto, the lower end of one wall of said core chamber being cut back to define a groove with the bottom of said lower mold part of lesser width than the thickness of a grain of molding sand, said lower part being formed with vent and blow out passages therein opening to said groove.

9. A blow tip for a sand core mold comprising a horizontally elongated body of abrasion resistant material and having continuously downwardly converging side Walls defining a downwardly tapering slot, horizontally spaced lateral projections on the outer side of one wall of said body arranged to contact a supporting surface and space said one wall from said surface by a distance less than the thickness of a grain of molding sand to form a vent passage, and a laterally projecting flange on the top of said body overhanging said vent passage and having a downwrdly opening recess on its underside opening between said vent passage and the edge of said flange, the Walls of said body being thicker at the bottom of said slot than at the top thereof.

10. A blow tip for a sand core mold comprising a horizontally elongated body of abrasion resistant material and having continuously downwardly converging side walls defining a downwardly tapering slot, horizontally spaced lateral projections on the outer side of one wall of said body arranged to contact a supporting surface and space said one wall from said surface by a distance less than the thickness of a grain of molding sand to form a vent passage, and a downwardly concave recess on the bottom of said body curved transversely of said slot.

11. A blow tip for a sand core mold comprising a horizontally elongated body of abrasion resistant material and having downwardly converging side Walls defining a downwardly tapering slot, and horizontally spaced lateral projections on the outer side of one wall of said body arranged to contact a supporting surface and space said one wall from said surface by a distance less than the thickness of a grain of molding sand to form a vent passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,049,732 Blake Aug. 1936 2,532,655 Backer Dec. :1, 1950 2,605,596 Uhri Aug. 5, 1952 2,688,780 Anderson Sept. 14, 1954 2,807,064 Jay Sept. 24, 1957 2,864,134 Harrison Dec. 16, 1958 2,899,724 Peterson Aug. 18, 1959 

